Roller guide assemblies are required in order that the material being processed by the mill arrives at the next set of reducing rollers in the proper orientation and any unwanted twisting of the material being reduced is prevented. Because mill operators are constantly under pressure to increase the output of an operating mill, the speed at which the material undergoing reduction continues to increase. Thus, if a billet is passed through a multi-stage reducing mill at ever increasing speeds, the last set of reducing rollers and the associated mill guides must be capable of rotational speeds to match the speed of the material exiting from the last reducing rollers.
The rollers in the guide usually have a predetermined shape to assure that the previously shaped material is grasped between the opposing guide rollers in a specific orientation to assure that the moving material is passed into the bite of the next set of rollers in a specific orientation. The rollers are usually mounted on bearing assemblies to enable the rollers to continuously rotate at fairly high speeds while sustaining substantial thrust due to the pressing engagement with the moving material. Because the rollers must rotate in an environment which may be best described as hostile, any suggestion of a mill operation, wherein the throughput is to be substantially increased by increasing the speed of the material being reduced, will be met with resistance and cynicism by mill designers. Because the material being reduced is hot, the rollers must be cooled in some manner to obtain a satisfactory bearing life for the bearings in the roller. The lead end of the material being reduced, may at times, strike one of the guide rollers upon entry to the guide causing a permanent scar on the surface of the roller and simultaneously cause a spike load on the bearing elements themselves which may cause a shortening of the life of the bearing.
It would seem obvious that the designers of steel mills could extend the life of the various components of the mill especially the guide members by decreasing the loading on the guide rollers and their bearings by the utilization of larger more robust rollers mounted on suitable bearings. Of course this avenue is not available because of the limited space available for the guide in the space between the rollers of each reducing stage. Thus, it is necessary to keep the roller diameter within certain prescribed limits to mount the guide as close to the roller byte as possible.